Arduino Function: RobotControl.playFile

Description

Play an audio file stored on a SD card.
The file type must be .sqm
The funtions Robot.beginSpeaker() and Robot.beginSD() are required in setup() before using this method.
Unlike Robot.playMelody() and Robot.playBeep(), playFile() does not halt other processes while playing. However, you cannot load new images on the LCD screen when playFile() is in use.
Valid files for playback are generated/converted by the sound library Squawk. See the library README for details on how to create your own music.